1. Field of the Invention
The present invention relates in general to centrifugal and mixed flow turbomachine (pumps, blowers and compressors), and relates in particular to diffuser turbomachine that can operate over a wide flow rate range by avoiding flow instability generated at low flow rates.
2. Description of the Related Art
When a centrifugal or mixed flow turbomachine is operated at low flow rates, stream separation can occur in some parts of the fluid compression system, such as the impeller and the diffuser, thus leading to a reduction in a pressure increase factor for a given flow rate, and producing a phenomenon of flow instability (rotating stall and surge) to make the system inoperable.
A current effort to resolve this problem involves maintaining minimum flow rate by providing bypass pipes or blow-off valves in the system so that the supply of fluid to the equipment to be operated is reduced. However, the volume of flow in the impeller of the turbomachine remains unchanged, thus presenting a problem that energy is being consumed wastefully.